Tetracycline (TC) in the water environment always brings negative impacts on human health and ecosystem equilibrium. Here we report that the carbon dots (CDs)/g-C3N4/ZnO nanocomposite prepared by a facile impregnation-thermal method exhibits outstanding photocatalytic activities for the total photodegradation of TC. Notably, the 30 wt% g-C3N4/ZnO with introducing 4 mL CDs solution (500 mg/L) photocatalyst displays the best photocatalytic.activity in the degradation of TC (100 mL, 10 mg/L; 100% degradation within 30 min) under very weak visible irradiation (lambda > 420 nm, 18 mW/cm(2)). In present system, CDs deposited on the surfaces of g-C3N4/ZnO heterojunction not only increases the visible-light response, but also promotes the efficiency of electron-hole pairs separation due to its electrons transfer property. Experiments further confirm that the superoxide radical (O-2(.)-) and hydroxyl radical ((OH)-O-.) formed on the surface of the photocatalyst are in charge of the degradation of TC. (C) 2016 Elsevier B.V. All rights reserved.